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We have investigated the spectral responsivity of porous silicon Schottky barrier photodetectors in the wavelength range 0.4-1.7 mum . The photodetectors show strong photoresponsivity in both the visible and the infrared bands, especially at 1.55 mum . The photocurrent can reach 1.8 mA at a reverse bias of 6 V under illumination by a 1.55-mum , 10-mW laser diode. The corresponding quantum efficiency is 14.4%.

The optical properties of electrodeposited Zn-ZnO structures annealed at different temperature in oxygen ambient are studied. Zn and ZnO coexist in all samples measured by x-ray diffraction, but only ZnO is observed for a sample annealed at 800 °C. From photoluminescence analyses, green and orange-red emissions are observed from an as-prepared sample. The spectrum is almost the same for the sample annealed at 300 °C. It shows a strong ultraviolet (UV) emission at the wavelength of 374 nm for the annealing temperature of 500 °C; the UV emission redshifts to 384 nm for the annealing temperature of 800 °C. The existence of metallic Zn crystals in ZnO plays a significant role in the emission characteristics.

As-grown and oxygen-annealed titanium oxide films grown on silicon substrate were studied. The titanium oxide films were prepared by metalorganic chemical vapour deposition in the temperature range of 400-650 • C. Compared with as-grown titanium oxide films, the oxygen-annealed titanium oxide films have better electrical properties and the stoichiometry of the titanium oxide film dominates the electrical properties. The leakage current can reach 2 × 10 −7 A cm −2 under an applied field of 5 MV. The hysteresis loop shift voltage and interface state density are 6 mV and 2.6 × 10 11 cm −2 eV −1 , respectively.

Metal–semiconductor Au–ZnO and Pt–ZnO films were prepared for enhancing ZnO photocatalytic activity. To increase the photocatalytic area in a metal–semiconductor material system, we introduce an efficient method where the metal and semiconductor are codeposited by an electrochemical method. The photocatalytic activity of Au–ZnO shows a better performance than that of Pt–ZnO determined by the degradation ability of methelene blue. There is an optimized Au concentration (∼2%) in Au–ZnO film for its best photocatalytic activity.